DNA - LAN Automation - Migrate Brownfield network to SDA Fabric

[robertbrink1]

I wonder if LAN Automation can be used to migrate an existing/brownfield network to become SDA Fabric. We intend to introduce two new nodes with border and control plane functionality and peer these with the current core network. (Hybrid migration, picture shows only one).

All edge switches that must be converted to fabric edge are connected to a distribution switch, physically. Between distro and core there is layer 3, but between distro and edge we use layer 2. The distro switches are just meant to be intermediate devices in the future fabric. 

The question is, can today's distribution switches become PnP seed devices (without becoming part of the fabric) and convert edge switches to fabric edge with the help of Lan Automation?

(LAN automation converts Layer 2 links to Layer 3 IS-IS links and provisions the edge to be sda fabric ready)

Picture shows the topology. Blue lines are layer 2, red are layer 3. 
Grey devices are legacy network. 

I wanted to test this in dCloud, but there was no slots available for quite some time. 

[rasmus.elmholt]

You should be able to use the left Dist switch as a seed device as long as the requirements for LAN automation are OK. And then reset the new FE switch and automate it.

Then you just need to make sure the DIST and CORE and BN are all part of the the same Routing domain.

[PabMar]

Hi Robert,

What's the L3 protocol between Border, core, disti?

If you do LAN Auto between disti and the new Edge device, it will be done in ISIS, then you'll have to redistribute ISIS into your existing L3 protocol. Not very clean.

I'd suggest you onboard the FE as a brownfield. Manually configure L3 between the disti and new Edge with your existing L3 protocol and then discover it from DNAC using the discovery workflow.

Regards.

[robertbrink1]

Hi, thx for the answer.

We have OSPF (point-to-point) between core and dist. And BGP as the main routing protocol. 

So this is a possible way of doing it when the ROI-value of LAN automation is greater than the "cleanliness"?

[PabMar]

Well there's no good RoI/Value if you have to manage 2 IGPs within the same site (adds mgmt, redistribution, tshoot gets more complex, etc). You'd end up with OSPF border-to-core-to-Disti and then ISIS Disti-to-Access.

If you want to leverage the LAN-Automation feature I personally would run it from Border all the way to access. So you would have to run it twice (as LAN-Auto runs up to two hops at a time). Border being the seed, it will configure Border-Core-Disti with ISIS, then start it again and make Disti as seed. That will close the loop and have ISIS all the way from Border to Access. This will require downtime however as you'll be replacing OSPF with ISIS on the site.

As you add more Fabric edge devices, you then run LAN-Auto from disti as seed to add new edges to the ISIS domain.

Hope that helps.

Regards.

[robertbrink1]

Thanks Pabmar, that helps. We'll need to go back to the "thinking-box" with this one. Hehe

Brownfield and SDA.. not that easy.